Patent GB-617876-A (GB)
Title: Improvements in and relating to devices for controlling the unwinding of a web of paper or the like from a roll thereof
IPC: B65H23/18
Filed: 1945-08-29
Abstract: 617,876. Feeding webs. KOLOK MANUFACTURING CO., Ltd., and LANT, R. Aug. 29, 1945, No. 22291. [Class 100(i)] A device for controlling the unwinding of a web of paper or the like from a roll so as to maintain constant web tension, comprises a pivoted arm with a roller bearing on the roll surface, the pivot being equidistant from the roll axis and the point of contact with the surface and the arm being secured to a shaft in driving connection with a member to which is secured a brake band or shoes co-operating with a drum on the roll shaft or a shaft secured thereto, and a loaded arm in driving connection with the pivoted arm in such a way as to maintain an angle with the vertical which is half the angle between lines joining the arm pivot with the roll axis and the point of contact with the roll surface, the brake thereby producing a resistance decreasing with the roll diameter. A standard 4, Fig. 2, on which are mounted in bearings 9, 11, for rotation together, a shaft 6a, Figs. 2 and 4, and a shaft 6 carrying a paper web roll 7, is mounted pivotally on a base 1 forming part of a paper coating machine and connected by bars 5 to a second standard slidable on a sole plate, so that the shaft 6 can be aligned with a shaft operating to draw the paper from the roll. A roller 33 on a pivoted arm 30 carried on a shaft 26 is urged against the roll surface by a counterweight 35, and a torsion spring 28 allows it to be withdrawn to insert a new roll. The shaft 26 is geared to a toothed sector 21 secured to a collar 22 freely rotatable on the shaft 6a, by means of pinions 23, 24 or pinion 23a, according to the direction of rotation of the roll, so that in either direction the sector 21 becomes more nearly vertical as the roll diameter diecreases. A brake drum 12 is mounted on the shaft 6a and co-operates with brake shoes 13 carried on a member 16 secured to a collar 20 freely rotatable on the shaft 6a and carrying an arm 36 to which is secured a weight 37 adjustable in respect of the length of the arm 36, according to the tension desired. The toothed sector 21 carries friction discs 44, 44a continuously and oppositely rotated by a flexible shaft 41 through pinions 40, 40a. The member 16 carries a spindle 51 on which is mounted a friction disc 45 contacting one or the other of the discs 44, 44a, with a slight clearance allowing a little freedom of relative rotation of the members 16, 21. The gearing between the sector 21 and shaft 26 is such as to maintain the arm 36 at half the angle to the vertical of the arm 30, whereby, the weight 37 opposing the torque of the brake drum on the brake shoes, the latter is diminished with the roll diameter to maintain constant tension. Minor variations in tension cause the disc 45 to hunt between the discs 44, 44a, with resultant rotation, in one or the other direction, of the spindle 51, which carries a worm 47 engaging a worm-wheel 48 which operates to tighten or loosen the brake shoes and rectify the variation. To avoid excessive tightening of the shoes on decrease in tension due to breaking of the web, the spindle 51 is threaded and carries a non- rotatable nut 52 in a guide 53, so that when the nut reaches an end of the guide, the shaft is moved axially and pulls the disc 45 out of engagement. A hand-wheel 46a on the spindle 51 enables the shoes to be loosened to allow initial feeding of the paper to the unwinding mechanism. A pin 56 attached to the member 16 may engage a hole in a yoke piece 58 on the sector 51, to maintain the device out of operative position. According to the Provisional Specification, the arm 36 may be set at a slight angle for zero setting of the arm 30 to compensate for the effect on the web tension of the friction of the bearings of the shaft 6.